1. Field of the Invention
The invention relates generally to the field of drilling wellbores through the Earth's subsurface. More particularly, the invention relates to systems for monitoring various drilling unit operating parameters during drilling unit installation and removal procedures.
2. Background Art
The current cost of drilling operations, particularly those in marine environments, has risen dramatically in recent years. Some deep water mobile offshore drilling unit (“rig”) operations cost in excess of $25,000 per hour. Such costs are making apparent the need for increased rig efficiency. Improving efficiency creates a need for measurement techniques related in particular to the time spent performing various functions on the rig. Generally, when referring to “drilling rig operations” and their related efficiency, those skilled in the art mean the time spent performing functions related to creating, deepening (lengthening) the drill hole or wellbore, and completing the wellbore. Such rig operations include, for example, rotary drilling with the drill bit “on bottom” (contacting the bottom of the wellbore) during sliding, “slide drilling” with directional drilling devices to alter the trajectory of the wellbore, tubular “tripping” (removing and inserting a pipe “string” from and into the wellbore) times, conditioning the hole and responding to downhole conditions. Efforts are often focused on measuring and improving the foregoing operations to obtain efficiency gains. For the sake of convenience the foregoing will be referred to as “drilling times.”
Recent automatic technology has allowed for drilling times to be characterized automatically and analyzed using sensors and software programs to determine the rig's actual operation at any moment in time. Recent examples of such automated monitoring technology are described in U.S. Pat. Nos. 6,892,812 and 6,820,702. The systems and method described in the foregoing patents relate to the automatic detection and measurement of times when the rig is conducting drilling operations, primarily as explained above.
Time when rig functions are characterized as “non-drilling” or “Flat Times” include such mobile drilling unit functions as mooring the rig, jacking up the rig, preloading/ballasting, skidding the drilling package, nippling up/testing BOP's (blowout preventers), running and testing marine drilling riser, testing the choke and kill lines, installing the slip joint and diverter, slip and cut drill line, setting back the top drive and rigging up to cement casing as well as non drilling times such as during well completion operations. The foregoing are not currently being automatically detected, measured, and analyzed as described in the above patents specifically because they relate to operations other than drilling.
Non-drilling times are usually harder to measure due to lack of sensors and automatic detection technology to facilitate measurement. Additionally, the lack of easily identified and measured “start/stop” points of a particular non drilling time function hampers measurement. Non-drilling times durations are often bundled together with several other “non-drilling” events and captured in a lump time on the daily report of drilling activity, for example, “Rig up & run casing, cement same, install wellhead and nipple up BOP's”. Such aggregated times often do not reflect the time spent performing individual activities, making it difficult to identify and measure inefficiencies and take action to correct such inefficiencies.
These non-drilling times are significant, for example, non-drilling time in a floating drilling platform can make up more than half of the total time included in drilling and completing a wellbore. Jackup drilling units, bottom supported (“platform”) drilling units and land-based drilling units use smaller amounts of such non-drilling times than do floating drilling platforms but all the foregoing still experience significant non-drilling times.
Significant rig time savings of these non drilling times were obtained when efficiency efforts including dedicated personnel went to the drilling unit with the goal of improving rig efficiency. Techniques used included manual characterization and analysis of the non-drilling times, and proposed modification of rig operations to correct inefficiencies. Efficiency improvements have been achieved with the foregoing manual method, wherein one-third improvement in non drilling times was common and some improvements of more than half have been recorded. As a practical matter, once the efficiency personnel left the drilling unit and no longer manually recorded start and stop times of the non-drilling operations, the efficiency gains typically dissipated, as personnel on the drilling unit had no device by which to measure and optimize the non-drilling operations times and the operations revert to their normal routine.
There continues to be a need to automatically measure, characterize and display for analysis the amounts of time spent on various non-drilling activities on drilling units especially offshore drilling units